Some internal combustion engines for automobiles have a tubular liner attached to an exhaust port of a cylinder head so as to cover the inner surface thereof in order to provide high temperature exhaust gas to an exhaust purification device incorporated in the exhaust system. These internal combustion engines can have an air layer (gap) between the liner and the exhaust port to suppress heat transfer from the exhaust gas to the cylinder head and maintain the temperature of the exhaust gas that flows into an exhaust purification device at a high temperature.
In order to positively attach such a liner to an exhaust port having curves and bends, the liner is divided into an upstream side and a downstream side, and both liners are inserted and attached separately from either an opening end on the upstream side or an opening end on the downstream side of the exhaust port. In the cylinder heads of some engines, the interior ends of the two liners mutually engage to form a continuous channel.
However, if the liner is divided into two parts inserted from the opposite ends of the exhaust port, positively connecting (engaging) the two liners together in the exhaust port is difficult. This is because the liner is positioned with a gap between the inner surface of the exhaust port and the liner, and therefore can easily displace. Thus determining the position of both interior ends of the liners is difficult.